A cassette tape for a cassette tape recorder has four tracks as shown in FIG. 1 in case it is used for a two channel stereo cassette tape recorder. When the tape 1 runs in a forward direction as shown at an arrow in FIG. 1, two lower adjacent tracks L.sub.1 (left channel) and R.sub.1 (right channel) are used, and when it runs in a reverse direction that is a direction reverse to that as shown at the arrow in FIG. 1, two upper adjacent tracks L.sub.2 (left channel) and R.sub.2 (right channel) are used.
In case that the cassette tape is used in a non-reversible tape recorder, record and/or playback can be accomplished at the lower and upper tracks by turning over the cassette in which the tape 1 is contained.
Also, it is noted that the tape cassette can be used in a reversible cassette tape recorder in which record and/or playback can be accomplished at the lower and upper tracks by reversing the running direction of the tape 1 without turning over the cassette. FIG. 2 shows one idea of head configuration for the reversible stereo cassette tape recorder having each exclusive operating gap for erase, record, or playback. In FIG. 2, head groups are disposed between pinch rollers P.sub.1 and P.sub.2 which are introduced into the cassette (not shown) through respective outside openings of five front openings thereof. A pair of heads H.sub.1 and H.sub.2 serving as recording and reproducing heads are introduced into the cassette through the center one of the openings of them and a pair of heads H.sub.3 and H.sub.4 serving as erasing heads are introduced into the cassette through respective remaining cassette openings. When the heads H.sub.1, H.sub.2, H.sub.3 and H.sub.4 are introduced into the cassette, they engage the tape 1 in the cassette. The erasing head H.sub.3 has an operating gap corresponding to the tracks L.sub.1 and R.sub.1 of the tape 1 while the erasing head H.sub.4 has an operating gap corresponding to the tracks L.sub.2 and R.sub.2 of the tape 1. The head H.sub.1 has four operating gaps in line of which two lower gaps are recording gaps g.sub.1 and g.sub.2 corresponding to the tracks L.sub.1 and R.sub.1 of the tape 1 and the two upper gaps are reproducing gaps g.sub.3 and g.sub.4 corresponding to the tracks R.sub.2 and L.sub.2 of the tape 1 while the head H.sub.2 has four operating gaps in line of which two lower gaps are reproducing gaps g.sub.3 and g.sub.4 corresponding to the tracks R.sub.1 and L.sub.1 of the tape 1 and the two upper gaps are recording gaps g.sub.1 and g.sub.2 corresponding to the tracks L.sub.2 and R.sub.2 of the tape 1. It will be noted that the heads H.sub.1 and H.sub.2 are disposed in a symmetrical manner relative to the position of recording and reproducing gaps.
When the tape 1 runs in the forward direction, the operating gap of the erasing head H.sub.3, the operating gaps g.sub.1 and g.sub.2 of the head H.sub.1 and the operating gaps g.sub.3 and g.sub.4 of the head H.sub.2 are in the operating condition. When the tape 1 runs in the reverse direction, the operating gap of the erasing head H.sub.4, the operating gaps g.sub.1 and g.sub.2 of the head H.sub.2 and the operating gaps g.sub.3 and g.sub.4 of the head H.sub.1 are in the operating condition. Thus, this head configuration may be embodied in a three-head type of reversible cassette tape recorder in which record or playback is made by each exclusive operating gap and a recorded signal can be monitored by reproducing gaps. In practice, it is easy to manufacture a conventional magnetic head having four gaps which are in line and have the same gap length and to use such magnetic head as each head H.sub.1 and H.sub.2.
However, for obtaining an excellent record and playback characteristic, it is desired that a gap length for recording gap is large (about 3 microns, for example), while a gap length of reproducing gap is small (about 0.6 microns, for example).